RT Journal Article
SR Electronic
T1 Interception of Excited Vibrational Quantum States by O2 in Atmospheric Association Reactions
JF Science
JO Science
FD American Association for the Advancement of Science
SP 1066
OP 1069
DO 10.1126/science.1224106
VO 337
IS 6098
A1 Glowacki, David R.
A1 Lockhart, James
A1 Blitz, Mark A.
A1 Klippenstein, Stephen J.
A1 Pilling, Michael J.
A1 Robertson, Struan H.
A1 Seakins, Paul W.
YR 2012
UL http://science.sciencemag.org/content/337/6098/1066.abstract
AB Bimolecular reactions in Earth’s atmosphere are generally assumed to proceed between reactants whose internal quantum states are fully thermally relaxed. Here, we highlight a dramatic role for vibrationally excited bimolecular reactants in the oxidation of acetylene. The reaction proceeds by preliminary adduct formation between the alkyne and OH radical, with subsequent O2 addition. Using a detailed theoretical model, we show that the product-branching ratio is determined by the excited vibrational quantum-state distribution of the adduct at the moment it reacts with O2. Experimentally, we found that under the simulated atmospheric conditions O2 intercepts ~25% of the excited adducts before their vibrational quantum states have fully relaxed. Analogous interception of excited-state radicals by O2 is likely common to a range of atmospheric reactions that proceed through peroxy complexes.